1. Field of the Invention
The present invention relates to an image recording method and an image recording apparatus, and more especially to an image recording method and an image recoding apparatus for, e.g., an apparatus for performing main-scanning of a recording medium to be sub-scanned and transferred, and then recording an image, in which the image is dispersion-recorded in a direction of sub-scanning.
2. Description of the Related Art
Conventionally, an image recording apparatus using a thermal head to record an image on a recording medium, has widely been used. Image recording apparatus like this, a thermal recording material, which is used for the recording medium, is pressed onto a line-type thermal head on which a plurality of heating elements are arranged in one-dimensional direction. While the heating elements are being controlled respectively in response to image data, the thermal recording material is transferred in a direction perpendicular to the one-dimensional direction, resulting in recording a desired two-dimensional gradation image.
In this case, the gradation image is formed as shown in FIG. 3A. Namely, the image of gradation D=1 is formed by activating the heating element or elements for t [seconds]. Further, the image of gradation D=2 is formed by activating the heating elements for 2t [seconds]. Further, the images of gradation D=3 to D=5 are formed by activating the heating elements for 3t to 5t [seconds], respectively.
Thus, pixels having different light-emission areas in accordance with gradation are formed on the thermal recording medium within a single pixel width in the transferring direction, as shown in FIG. 3B. Thereby, a gradation image is recorded. In the above example, a case of modulation of the pulse width has been described. However, even in a case of modulation of a number of pulses, a gradation image is recorded in substantially the same manner as in a case of modulation of the pulse width as above.
Incidentally, when a gradation image is recorded like this, each pixel is always recorded from a constant point (point xe2x80x9caxe2x80x9d in FIG. 3B). Since the point xe2x80x9cbxe2x80x9d side in a single pixel width in the transferring direction becomes no-recorded portion, the recorded image becomes concentrated on the point xe2x80x9caxe2x80x9d side as above. Therefore, when a formed two-dimensional image is viewed over its entirety, there occurs a drawback that the image becomes conspicuously coarse.
In order to overcome this drawback, it is effective to dispersion-record the image data. Various types of technologies therefor have been proposed. For example, the technology of xe2x80x9cImage Recording Method and Apparatusxe2x80x9d disclosed in JP 07-96625 A corresponded to an application made by the assignee for the present invention also can be given as one example of such a technology.
According to this technology, when the image is one-dimensionally recorded along in a one-dimension direction on the recording medium using an image recording unit, and either the recording medium or the image recording unit is moved in a direction perpendicular to the one-dimensional direction to record the image, and simultaneously, the multi-gradation image data of each of pixels constituting the image are divided into a plurality of substantially equal portions of image data. Based on this plurality of divided image data, the image is dispersed in a direction in which the recording medium or the image recording unit, is moved and thus recorded.
According to this technology, the image data of each of the pixels constituting the image is divided into a plurality of substantially equal portions of image data. Based on the divided image data, the image is dispersed in a direction in which the recording medium or the image recording unit is moved thereby recording the image. This produces the result that the roughness occurred in recording the two-dimensional gradation image disappears, and it becomes possible to record an image with high image quality.
Further, in a technology of xe2x80x9cImage Recording Methodxe2x80x9d disclosed in JP 10-44509 A corresponded to an application which was also filed by the same assignee for the present application, an image is recorded using an image recording unit in a one-dimensional manner onto a recording medium, and also, either the recording medium or the image recording unit is moved in a direction perpendicular to the one-dimensional direction to record the image, and multi-gradation image data of the image elements constituting the image are divided into a plurality of number of substantially equal portions of image data. This image data is allotted to a part of the recording points divided by a number of the image data or more. Then, the image is dispersed in the moving direction in which the recording unit or the image recording unit is moved thereby recording the image.
According to this technology, it becomes possible to prevent deterioration such fuzziness of the image quality in the low density areas, in which there has been a possibility of such deterioration occurring in the technology discussed above, and this makes it possible to apply the image dispersion-recording method more effectively.
However, recently, an image to be recorded has been formed by higher steps of gradation than ever. For example, 4,096 steps of gradation form a 12-bit-image. Accompanying with such an improvement, when a thermal recording is performed using the dispersion-recording technology, a further problem has occurred that a number of data-transfer is being increased.
The present invention is developed in view of the above-mentioned problem. The invention has an object to provide an image recording method and apparatus capable of overcoming the problem owing to that the number of data-transfer has been increased when an image is formed using higher steps of gradation in the above-mentioned dispersion-recording technology.
One aspect of an image recording method relating to the present invention is characterized in that the image recording method of recording a single pixel forming an image using a plurality of pulses comprises the step of expressing gradation using a single pulse or a plurality of pulses expressing a superordination bit having larger pulse width and a single pulse or a plurality of pulses expressing a subordination bit having smaller pulse width.
It is further preferable the image recording method in which the plurality of pulses at irregular intervals are applied to the single pixel. Additionally, the plurality of pulses at irregular intervals are applied to not only the single pixel but also neighboring pixels.
Further aspect of an image recording method relating to the present invention is characterized by having activation (ON-status) or non-activation (OFF-status) for each of the pulses, related to a specified bit forming image data.
Further aspect of an image recording method relating to the present invention is characterized by expressing gradation using a single pulse or a plurality of pulses having a larger pulse width expressing a superordination bit and a single pulse or a plurality of pulses having a smaller pulse width expressing a subordination bit and having activation or non-activation operation for each of the pulses, related to a specified bit forming image data.
One aspect of an image recording apparatus relating to the present invention is characterized by having an image recording unit which records an image in a first direction; a transfer unit which relatively transfers said image recording unit and a recording medium in a second direction normal to said first direction; and a record control unit which controls and records a single pixel using a plurality of pulses when the image is recorded, the record control unit expressing gradation for the image to be recorded using one pulse or more each whose pulse width is greater expressing a superordination bit and whose pulse width is smaller expressing a subordination bit.
Further aspect of the image recording apparatus relating to the present invention is characterized in that the plurality of pulses at irregular intervals are applied to the single pixel. Additionally, the plurality of pulses at irregular intervals are applied to not only the single pixel but also neighboring pixels.
Further aspect of the image recording apparatus relating to the present invention is characterized by having an image recording unit which records an image in a first direction; a transfer unit which relatively transfers the image recording unit and a recording medium in a second direction normal to the first direction; and a record control unit which controls and records a single pixel using a plurality of pulses when the image is recorded, the record control unit having activation (ON) or non-activation (OFF) operation for each of the pulses, related to a specified bit forming image data.
Further aspect of the image recording apparatus relating to the present invention is characterized by having an image recording unit which records an image in a first direction; a transfer unit which relatively transfers the image recording unit and a recording medium in a second direction normal to the first direction; and a record control unit which controls and records a single pixel using a plurality of pulses when the image is recorded, the record control unit expressing gradation for the image to be recorded using a single pulse or a plurality of pulses having a larger pulse width expressing a superordination bit and a single pulse or a plurality of pulses having a smaller pulse width expressing a subordination bit and having activation or non-activation operation for each of the pulses, related to a specified bit forming image data.
Additionally, the above image recording apparatus includes a thermal head.